Mass Media Interventions to Reduce Youth Smoking is a program project that will develop methods of design and delivery of comprehensive, theory-based media campaigns to reduce the prevalence of cigarette smoking among ethnically diverse adolescents, and to assess the effects of these methods on the prevention and cessation of tobacco use among these targeted population. This will be accomplished through the close integration of three research projects. Project 1, Message Development Using Audience Research, will apply diagnostic and formative research methods with ethnically/racially diverse populations of adolescents to inform the development of theory- based smoking prevention and cessation messages for media campaigns. Message content than will be tested with studies according to grade, gender, racial/ethnic identity, and smoking risk to help define audience segments for targeting smoking prevention and cessation interventions. Project 2, Reducing Youth Smoking Using Mass Media, will develop media messages in four-year campaigns designed to prevent smoking among adolescents and will evaluate their effectiveness in four intervention mass media markets versus four comparison areas. Project 3, Youth Smoking Cessation Using Mass Media, will develop mass media messages in a three-year campaign designed to help adolescents stop smoking and will evaluate their effectiveness with a cohort of weekly smokers established at baseline in four intervention mass media markets and in four comparison areas.